Laser beveling process for catheters

ABSTRACT

A process and product and apparatus are disclosed wherein a laser is used to form a conical tapered tip on a catheter product. The catheter is placed on an insertion needle prior to the formation process, thus eliminating the problems associated with wearing out forming tooling. The process and product further call for the use of the laser to create a surface effect on the cannula to indicate the terminus of the catheter.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for formingcatheter products and particularly to a method and apparatus forbeveling the tip of intravenous catheters.

Intravenous catheters come substantially in two types of products. Thefirst type is a through-the-needle catheter product wherein the catheterthat is to be disposed within the vein is inserted through a sharpenedcannula. The cannula is used to pierce the skin and insert the catheterand later is removed. However, this type of catheter has not met withmuch commercial success do to inherent flaws in the through-the-needletype delivery system. For example, the needle must be larger in diameterthan the catheter being inserted. Therefore, the needle creates a largeropening on insertion than the catheter requires and creates a greaterchance of leakage. Furthermore, it is difficult to remove and dispose ofthe needle or cannula once the catheter has been inserted.

The second and more common type of intravenous catheters is theover-the-needle catheter. In this type of product a needle or cannulahas disposed thereover a catheter. The catheter is disposed such thatthe sharpened tip of the needle is extending from the catheter productand is used to pierce the patient's skin and insert the catheter. Oncethe skin and vein have been pierced, the catheter is threaded off of theneedle and the needle is removed from the catheter product.

In order to ease the insertion of the over-the-needle type catheterproducts, it has long been known to bevel the tip of the catheter toprovide a smooth transition between the surface or outer diameter of theneedle or cannula and the surface or outer diameter of the catheteritself during the insertion process. There have been many methodsdeveloped for beveling the tips of catheters. For example, U.S. Pat. No.4,661,300 to Daugherty entitled "Method and Apparatus for FlashlessTipping of an I.V. Catheter" discloses a process which was used in theearly 1980's to mold a beveled tip on a catheter while simultaneouslytrimming the flash in order to provide a clean edge to the tip. Thisprocess, however, requires a high cost in retooling because of the wearinterface between the two tool members and the cleaning necessary tounclog the mold from the trimmed flash.

Catheters have also been provided with what is actually a duel bevel.The bevel begins gently at approximately 3° and then is sharper right atthe tip, for example 27°. The sharper bevel is provided to ease thetransition to the initial OD of the catheter, while the softer beveleases the opening to the final OD of the catheter.

SUMMARY OF THE INVENTION

Therefore, in order to eliminate the molding process of the prior art,the present invention provides for laser cutting or ablating of thepolymer material, which forms the tubular sheath of the catheter. Acatheter is normally formed of a hub of material for receiving a fittingat a proximal end of the catheter and a distal portion of tubularmaterial. This tubular material may be preformed with a slight bevel onthe outer surface with a final sharper bevel provided by the lasercutting process.

The process for beveling the tip comprises providing a source ofcoherent light such as laser light from an excimer laser, which hassufficient power to ablate, cut, melt or otherwise form the cathetermaterial. The catheter is positioned in a path where it will interceptthe coherent light and is rotated while positioned in that path. Bypositioning the catheter with the light path at an angle to the cathetermaterial, the rotation will form a frustoconical surface ofpredetermined angularity.

Preferably, the current process is carried out with the catheter alreadyin place on an insertion cannula or needle. Thus, the process may becontrolled such that the bevel is formed at the very heal or bottom ofthe sharpened point of the needle so that a natural transition occursbetween the sharpened point of the needle and the beginning of thecatheter material.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings wherein;

FIG. 1 is a perspective view of a catheter tip, including needle, madeaccording to the present invention;

FIG. 2 is a partial cross-sectional view of a catheter of the invention;

FIG. 3 is a schematic perspective view of a laser apparatus of thepresent invention;

FIG. 4 is a schematic representation of the handling process of thepresent invention;

FIG. 5 is a side elevation view of the apparatus of the presentinvention;

FIG. 6 is a top plan view of the positioning and handling portion of theapparatus;

FIG. 7 is a partially broken away view of the spinning portion of theapparatus;

FIG. 8 is a cross-sectional view of FIG. 7 taken along lines 8--8;

FIG. 9 is a cross-sectional view of FIG. 7 taken along lines 9--9;

FIG. 10 is a view taken along lines 10--10 of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Catheters are generally made of polymer materials and the substantialmajority of intravenous catheters are either made of apolytetrafluoroethelyene (PTFE) material, such as Teflon™ as sold by E.I. du Pont de Nemours and Company, 1007 Market Street, Wilmington, DE19898 and clear polyurethane materials. Certain polymers may be used toproduce an optically clear radio opaque catheter, which permits visualinspection of the internal volume, while it may be located through theuse of standard x-ray inspections.

The catheter includes a cannula 1, having a sharpened point 2, which isused to pierce the site of insertion of the catheter. The catheter 3 isdisposed over the cannula 1 and has a tip 4, which provides the initialtransition point between the cannula surface and the outer surface ofthe catheter. The catheter tip 4 is provided with a taper 5 and a bevel6. The cannula is also provided in the present invention with a zone 7,which provides visual indication of the tip of the catheter. Referringto FIG. 2 it is seen that during the process of forming the catheter,the taper angle Alpha (α), preferably approximately 3° but which mayrange from 1°-10° is formed on the tip of the catheter. A second angle,Beta (β), is formed at the end of the catheter tip in order to providethe transition between the surface of the cannula and the surface of thetaper.

As will be described below, the angle alpha is initially formed on thecatheter outer surface and the angle beta is formed by use of a lasercutting or ablation process which simultaneously removes the materialfrom the catheter tip forming the bevel and which makes the indicationzone 7 on the cannula.

Referring to FIG. 3, the source of this laser is indicated. As laser 10is provided, which is particularly an excimer laser. For example, theexcimer EX-748 laser as provided by Lumonics Inc. of Kanata, Ontario,Canada. The laser beam 11 is manipulated by mirrors 12 into a positionrunning adjacent to the manufacturing apparatus. A masking slide 13reduces the amount of energy provided ultimately to the apparatus bymasking a portion of the beam prior to its focusing. The masking slidealso acts as a preliminary beam shaping device to shape the beam priorto entering lens 14. Lenses 14 and 15 focus the beam and form a thinrectangular shape to the beam. Beam splitters 16 are provided, whichpermit passage of a certain percentage of the power while reflecting aninitial percentage, such that three beams are provided, each havingapproximately 1/3 of the power delivered through the lenses 14 and 15.

By acting on the power and shape of the beam the mask 13 and lenses 14and 15 can be used to shape the distal end of the catheter. Thepreferred embodiment of the mask is always 15 mm wide, that is, 15 mm inwidth across the beam. However, the height of the slit may be varied.The slit is rectangular and a preferred slit height is 0.8 mm. Thisprovides an opening which is 0.8 mm by 15 mm to initially shape thebeam. This preliminary shaped beam will provide a substantially flatconical surface to the catheter tip 4. An alternative embodiment createsa novel tip having a concave shape. This shape presents a softer profileto the entry point at the beginning of insertion and gradually increasesas the catheter is inserted. That is the angle of attack of the surfaceis very close to the outer circumference of the needle at the very endof the catheter but the further away from the tip the greater thediameter gets in a slightly curved fashion. To provide such a shape amask having a slit which is 3 mm high by 15 mm wide readily creates aconcave structure to the tip.

Successful operations of catheter tipping have been run usingpolyurethane material and a laser pulse repetition rate of 180-190pulses per second, with burst sizes ranging from 340-360 pulses. Thetotal energy applied has ranged from 300 to 325 millijoules. Althoughthese ranges were used experimentally, it is believed that much widerranges will be operable without being beyond the scope of thisinvention. Furthermore, the selection of a three-beam split from asingle beam is merely arbitrary in nature. A very small percentage ofthe total beam power is being used in the three-beam situation andtherefore additional beam splits could be used if desired from anindividual laser set up.

Referring to FIG. 4, there are shown the schematic set up of an assemblyand manufacturing apparatus for catheters of the invention. An initialfabrication set up and supply indicated schematically by areas 17 and 18is used to make conventional catheters. For example, a polyurethanecatheter attached to a polymer hub, which is placed on a sharpenedcannula for insertion. The initial fabrication of the catheter tube andhub may be the same as that currently used by those of ordinary skill inthe art. The catheter is formed either with the initial 3° taperindicated previously, or left as a straight tube. The catheter andneedle assembly is then removed from the fabrication machine by arm 19and placed on a carrier 20 on positioner 21. Positioner 21 has a seriesof carriages 22, each having positions for three catheter and cannulasubassemblies. The carriages are rotated about the positioner 21 as willbe described below and brought into a set position. The catheter andcannula subassembly is positioned where it will intercept one of thesplit beams 24 and is rotated at a given speed. For example, atapproximately three rotations per second. However, the rotation speedmay be at six rotations or higher. The catheter and cannula subassemblyis exposed to the laser for approximately 2 seconds. This time isdetermined by the pulse repetition rate and the energy of the laserbeam. The number of pulses being selected such that the speed of formingthe product is optimized while using an amount of energy that does notoverly heat the product or cause melting or other destruction of thetip.

During the impingement of the laser beam on the product, the cathetermaterial is ablated in a conical shape due to the rotation of thecatheter and cannula subassembly, and positioning such subassembly at a45°±2° angle to the laser beam direction, as shown in FIG. 5. Thisablation causes a release of polymer molecules and by-products, whichare removed from the manufacturing area through hood 25. If anexceptionally long catheter tube is used, it may be necessary to providea vacuum source at the tip of the cannula to pull any residual catheterportion above the zone of the laser impingement off the catheter andremove it from the cannula.

The catheter and cannula subassembly is rotated through the use of amotor and transmission subassembly, which is shown schematically in FIG.5. The motor 26 rotates the assemble through a transmission 27, and aclutch 28. The clutch 28 and motor assembly are moved vertically toengage the bottom of the carrier to rotate the catheter and cannulasubassembly. Although the speed of rotation is controlled, the point atwhich the clutch engages and disengages need not be controlled withfinite accuracy. The catheter and cannula subassembly is rotated and thetiming of the process is controlled by the initiation and termination ofthe laser impingement on the product. Therefore, the product is startedalong its rotational motion and then the laser is turned on to form thebeveled end. After the laser has been turned off, the clutch 28 motor 26and transmission 27 are dropped out of engagement with the carriage andthe carriage is repositioned. As can be seen more clearly in FIG. 7, thetransmission 27 provides a group of three clutches 28. The transmission27, through the use of a gear system indicated in FIG. 10, transmitspower to driven gears 31 through drive gear 30. Driven gears 31 aredriven at the same speed as drive gear 30, thus maintaining consistencyin the manufacturing operation.

The entire drive assembly 32, which consists of the transmissions, motorand clutch mechanisms is raised and lowered into engagement with theholders 33 in the carriage 20. Each holder 33 has provided thereon acatheter and cannula subassembly such that the raising of the driveassembly 32 engages the clutch 28 of each respective holder 33 andthereby drives the rotation of catheter and cannula subassembly (FIG.9). After formation of the bevel, the carriage is rotated out ofposition back to the start of the carrier 20 and arm 19 removes theproduct from the carriage and returns it to the assembly process forfinal assembly of the catheter. This assembly may merely require theaddition of a shield to the catheter product or may require furtherfabrication steps to make a desired final fabrication assembly.

By adjustment of the power and focus of the laser beam 11, a zone 7 maybe formed on the cannula surface. This zone is believed to be a surfacefinishing of the stainless steel cannula, which is the preferred cannulaused in the process. This cannula is a 304 stainless steel and it isbelieved that the laser either removes the natural oxidation from thesurface of the cannula and subsequently produces a zone with a higherconcentration of chromium than is found in the normal surface of thecannula. This zone can be manipulated to be of a significant size orvirtually non-existent. It has been found to preferably create a zone ofapproximately 1 mm inches wide, which provides a visual indication ofthe end of an optically clear catheter material.

Furthermore, it has been found that the catheter material may be lightlysealed to the outer surface of the cannula, thus reducing or preventingthe leakage of blood between the catheter and cannula during theinsertion process. This sealing has been provided with such limitedstrength that it does not significantly reduce the performance of theproduct in the removal of the cannula from the catheter.

The invention has been described in its preferred embodiment. It caneasily been seen by one of ordinary skill in the art that manymodifications may be made to the preferred embodiment without leavingthe scope of the invention.

We claim:
 1. A process for beveling a tip of a catheter having a tubularsheath and longitudinal axis comprising:a) providing a source ofcoherent light with sufficient power to ablate the catheter material; b)positioning said catheter in a path of said coherent light with saidlongitudinal axis at a predetermined angle to said path; and c) rotatingsaid catheter while impinging said coherent light on said catheter alonga predetermined path to ablate catheter material at a predetermined tiplocation to form a frusto conical tip surface.
 2. The process accordingto claim 1 wherein the catheter is positioned upon a cannula prior toimpinging coherent light on the catheter.
 3. The process according toclaim 2 wherein the coherent light impinges on the cannula surface andchanges the catheter surface in the area of impingement to differ fromthe remaining cannula surface.
 4. The process according to claim 1wherein the source of coherent light has a cross sectional shape andpower which ablates said catheter material in a concave shape.
 5. Theprocess according to claim 1 wherein the cross sectional shape end powerof the coherent light impinging on the catheter is shaped to create aconvex tip shape.
 6. The process according to claim 1 wherein saidpredetermined path is approximately 45° to a longitudinal axis of saidcatheter.
 7. The process according to claim 1 wherein said coherentlight is shaped by passing said beam through a slit mask.
 8. A processfor beveling a tip of a catheter having a tubular sheath comprising:a)providing a pre-molded tubular sheath having a predetermined bevel onthe outer surface thereof; b) positioning said catheter at apredetermined position; c) impinging an incident beam of coherent lightupon such catheter at a predetermined position an angle while rotatingsaid catheter to trim said catheter at said predetermined position.
 9. Aprocess according to claim 9 wherein said catheter is provided with aneedle therein and said incident beam of light is directed and focusedto change the surface of said needle during said trimming process. 10.The process according to claim 9 wherein the surface effect is toincrease reflectivity of the surface of said needle at a positionadjacent the end of said catheter.
 11. The process according to claim 10wherein said needle is stainless steel.
 12. A process for simultaneouslytrimming and providing surface effect to a catheter and needlerespectively comprising:a) positioning a catheter on a needle to providea catheter needle subassembly; b) positioning said catheter and needlesubassembly at a predetermined position; c) rotating said catheter andneedle subassembly at said predetermined position while impingingthereon a beam of coherent light of sufficient energy to ablate thecatheter substance; d) providing said beam of coherent light forsufficient time and at a predetermined angle to ablate the circumferenceof the catheter forming a bevel tip and to impinge upon the surface ofthe needle with sufficient energy to visually modify the surfacethereof.
 13. The process according to claim 12 wherein said surfaceeffect modifies the surface of said needle by removing an oxidized layerfrom the surface of said needle.
 14. The process according to claim 12wherein said needle is stainless steel.
 15. The process according toclaim 14 wherein said needle is 304 stainless steel.
 16. The processaccording to claim 12 wherein said surface effect modifies the surfaceof said needle by increasing the concentration of chromium at thesurface of a stainless steel needle.